In this chapter, authors Daniel Menasce and Virgilio A.F. Almeida start by providing
a clear definition of what capacity planning means, and then present a methodology
to help the capacity planner through the process of determining the most cost-effective
system configuration and networking topology.

5.1 Introduction

Planning the capacity of a C/S system requires that a series of steps be followed
in a systematic way. This chapter starts by providing a clear definition of
what adequate capacity means. It then presents a methodology that leads the
capacity planner, in a step-by-step fashion, through the process of determining
the most cost-effective system configuration and networking topology. Investment
and personnel plans follow as a consequence. The main steps of the methodology
are: understanding the environment, workload characterization, workload model
validation and calibration, performance model development, performance model
validation and calibration, workload forecasting, performance prediction, cost
model development, cost prediction, and cost/performance analysis.

The methodology presented here requires the use of three models: a workload
model, a performance model, and a cost model. The workload model captures the
resource demands and workload intensity characteristics of the load brought
to the system by the different types of transactions and requests. The performance
model is used to predict response times, utilizations, and throughputs, as a
function of the system description and workload parameters. The cost model accounts
for software, hardware, telecommunications, and support expenditures.

This chapter draws in part on material presented in [7] and Chap. 2 of [8].
Various steps of the methodology are discussed in further detail in subsequent
chapters.